CVE-2018-12123 in Node.js
Summary
by MITRE
Node.js: All versions prior to Node.js 6.15.0, 8.14.0, 10.14.0 and 11.3.0: Hostname spoofing in URL parser for javascript protocol: If a Node.js application is using url.parse() to determine the URL hostname, that hostname can be spoofed by using a mixed case "javascript:" (e.g. "javAscript:") protocol (other protocols are not affected). If security decisions are made about the URL based on the hostname, they may be incorrect.
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Analysis
by VulDB Data Team • 12/13/2024
The vulnerability identified as CVE-2018-12123 represents a hostname spoofing issue within Node.js URL parsing functionality that affects multiple versions prior to specific security releases. This flaw resides in the url.parse() method implementation where the JavaScript protocol handling exhibits case-insensitive parsing behavior that can be exploited to manipulate hostname determination. The vulnerability specifically targets applications that rely on url.parse() to make security-sensitive decisions based on URL hostnames, creating a potential attack vector where malicious actors can craft URLs with mixed-case protocol identifiers to bypass intended security checks.
The technical implementation flaw stems from how Node.js processes protocol identifiers in URL parsing operations. When a URL contains a protocol identifier with mixed case such as "javAscript:" instead of the standard "javascript:", the parsing logic fails to properly normalize or validate the protocol casing, allowing the parser to treat the mixed-case identifier as a valid protocol. This inconsistency in protocol handling creates a scenario where applications that depend on hostname verification for security purposes may incorrectly interpret the URL structure, leading to potential bypasses of access controls or security filters that rely on proper hostname validation.
This vulnerability operates under the broader category of protocol handling flaws and can be categorized under CWE-20: Improper Input Validation, specifically manifesting as a case sensitivity issue in protocol parsing. The operational impact extends beyond simple parsing errors to encompass security decision-making processes within Node.js applications, potentially enabling attackers to circumvent security controls that depend on URL hostname validation. The attack surface includes any application that uses url.parse() for security-related decisions, particularly those implementing access control, content filtering, or cross-origin resource sharing validation mechanisms.
The security implications of CVE-2018-12123 align with ATT&CK technique T1068: Exploitation for Privilege Escalation, where protocol manipulation can be used to bypass security controls. Applications that perform security checks based on URL hostnames, such as those implementing whitelist validation or origin-based access controls, become vulnerable to this attack vector. The vulnerability particularly affects systems where JavaScript protocol URLs are processed without proper validation, creating opportunities for attackers to craft malicious URLs that appear legitimate to security systems while actually containing spoofed hostnames.
Mitigation strategies for this vulnerability require immediate application updates to supported Node.js versions including 6.15.0, 8.14.0, 10.14.0, and 11.3.0 where the parsing behavior has been corrected. Organizations should implement additional input validation measures that explicitly check protocol case sensitivity and normalize protocol identifiers before processing URLs. Security teams should conduct comprehensive code reviews to identify all instances where url.parse() is used for security decisions, implementing proper validation layers that ensure hostname integrity regardless of protocol casing variations. Additionally, application-level protections should include explicit protocol validation that rejects URLs with non-standard protocol casing to prevent exploitation of this specific vulnerability.
The broader implications of this vulnerability highlight the importance of protocol normalization in web application security contexts and demonstrate how seemingly minor parsing inconsistencies can create significant security risks. This issue underscores the need for comprehensive security testing of URL parsing components and emphasizes the critical requirement for consistent protocol handling across all security-sensitive operations. Organizations should establish security guidelines that mandate proper URL validation practices and implement automated testing procedures to detect similar protocol handling vulnerabilities in their applications.